<em>import React from 'react'</em>

<em>export default ( <q>props</q> ) =></em> {
	<em>const action</em> = <q>props.history</q>.<b>action</b> 		<em>// 首次进入、前进、后退		=== </em> <b>POP</b>
										<em>// props.history.push( ) 		=== </em> <b>PUSH</b>
										<em>// props.history.replace( ) 	=== </em> <b>REPLACE</b>
	<em>return null</em>
}